At the same time the people who did take it seriously were also unfairly discredited. There was a legitimate theory of the psychedelic state as a "model psychosis" which was simply rejected during the anti-drug hysteria which followed.
The government (CIA) also used psychedelics in all kinds of horrible, torturous ways with their experiments.
It looks like this time around the experiments are much more controlled and looking to get hard data rather than just "turn on, tune in, drop out".